Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente. Drain and set aside, reserving about 1 cup of pasta water.

While the pasta is cooking, heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the chicken pieces and cook until golden brown and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.

Add the sliced mushrooms to the same skillet and cook until they release their liquid and turn golden brown, about 5-7 minutes. Add the chopped onion and cook until softened, about 3-4 minutes. Stir in the minced garlic, Italian seasoning, salt, and pepper, and cook for another minute until fragrant.

Pour in the chicken broth and bring to a simmer, scraping up any browned bits from the bottom of the skillet. Reduce the heat to low and stir in the heavy cream and grated Parmesan cheese. Cook, stirring constantly, until the cheese is melted and the sauce is smooth and slightly thickened. If the sauce is too thick, add a splash of the reserved pasta water until it reaches your desired consistency.

Return the cooked chicken to the skillet with the sauce. Add the drained pasta and toss gently to coat everything evenly. Cook for another 1-2 minutes, allowing the pasta to absorb the flavors. Serve immediately, garnished with fresh chopped parsley and extra Parmesan cheese, if desired.